- Generic name: cephalexin
- Brand names: Keflex,® Keftabs, Biocef
- Therapeutic class: Antibiotic
- Pharmacologic class: Cephalosporin, first-generation
- Pregnancy Category: B
- FDA Approved: January 4, 1971
- Chemical Formula: C16H17N3O4S
- Originally discovered: 1967, Eli Lilly Ltd, USA
- Respiratory tract infections caused by Streptococcus pneumoniae and Streptococcus pyogenes
- Otitis media due to Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcusaureus, Streptococcus pyogenes, and Moraxella catarrhalis
- Skin and skin structure infections caused by Staphylococcusaureus and/or Streptococcus pyogenes
- Bone infections caused by Staphylococcusaureus and/or Proteus mirabilis
- Genitourinary tract infections, including acute prostatitis, caused by Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae
- Gram-positive Aerobes: Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes
- Gram-negative Aerobeses: Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Proteus mirabilis
- Mastitis, a breast inflammation often caused by a blocked milk duct that hasn't cleared.
- Diverticulitis 5
- Excellent safety record
- Very low incidence of allergic reactions
- May be taken without regard to food
- Very high oral bioavailability
- Superior to penicillin in the streptococcal throat infection 2.
- Very effective for mild cases of cellulitis 3. Cephalexin remains the preferred antibiotic for the treatment of uncomplicated streptococcal cellulitis4.
- Active against most gram-positive bacteria.
- Short half-life requires QID dosing: the serum half-life is 0.5–1.2 hours in adults, about 5 hours in neonates and 2.5 hours in children 3–12 months of age.
- Less active than cefatrizine and cefaclor against Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis 2.
Cephalexin inhibits the third and last stage of bacterial cell wall synthesis by preferably binding to specific proteins (PBPs) that are located inside the bacterial cell wall.
Cephalexin mean half-life is 50 to 80 min. It may take 4 to 5 hours to clear out of the system.
- Cephalexin (Keflex) versus other medications
- 1. Disney FA, Dillon H, Blumer JL, Dudding BA, McLinn SE, Nelson DB, Selbst SM. Am J Dis Child. 1992 Nov;146(11):1324-7. PubMed
- 2. Luh KT, Chao HP, Ho SW, Hsieh WC. Comparison of in vitro antibacterial activity of four oral cephems. Zhonghua Min Guo Wei Sheng Wu Ji Mian Yi Xue Za Zhi. 1984 Feb;17(1):11-8. PubMed
- 3. Pallin DJ, Binder WD, Allen MB, Lederman M, Parmar S, Filbin MR, Hooper DC, Camargo CA Jr. Effectiveness of cephalexin plus TMP-SMX versus cephalexin alone for treatment of uncomplicated cellulitis: a randomized controlled trial.. Clin Infect Dis. 2013 Jun;56(12):1754-62 PubMed
- 4. Cunha BA. Cephalexin remains the preferred antibiotic for uncomplicated cellulitis. Journal of Chemotherapy. 2014 Apr;26(2):65-6.
- 5. Kevin R. Loughlin, Joyce A. Generali, Eds. (2006) The Guide to Off-Label Prescription Drugs New York: Free Press, p.702
Published: March 31, 2008
Last updated: July 20, 2017